Mini-measurement display for digital multimeter

ABSTRACT

A digital multimeter displays a miniature version of a live actual reading of the multimeter. The miniature version typically appears after a larger version of the live actual reading is displaced by other display elements. The miniature version of the live actual reading may be accompanied by a warning icon or other graphical symbol to alert a user of a potentially hazardous electrical condition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/838,881, filed Aug. 14, 2007, the disclosure of which ishereby incorporated by reference in its entirety. This applicationclaims priority under 35 U.S.C. §120 to U.S. patent application Ser. No.11/838,881.

BACKGROUND

Multimeters are used for measuring a variety of parameters associatedwith electrical circuitry, such as currents, voltages, resistances, andcapacitances. Multimeters commonly include rotary switches for selectingbetween different measurement functions. For example, a rotary switch ona conventional multimeter may be configured such that a first positionof the rotary switch corresponds to a voltage measurement function, asecond position of the rotary switch corresponds to a currentmeasurement function, and a third position of the rotary switchcorresponds to a resistance measurement function.

Modern digital multimeters commonly provide many different measurementfunctions. Accordingly, to save space on these multimeters, researchershave developed rotary switches where each position of the rotary switchcorresponds to more than one measurement function. As examples, a singleposition of a rotary switch may correspond to different units ofmeasurement, such as Amps (“A”) and milliamps (“mA”), or differentmeasurement types altogether, such as current measurement andtemperature measurement. These multimeters generally allow a user toswitch between the different measurement functions associated with aparticular position of the rotary switch by actuating a separate buttonor switch while maintaining the rotary switch in the same position.

Another feature found in modern digital multimeters enables a user toselect between different modes that affect what or how measurements areacquired, maintained, and displayed. For example, a user can select a“Minimum/Maximum” (Min/Max) mode, which updates a display with minimumand maximum detected measurement values. As another example, a user canselect a “Record” mode to record measurement values for memory storageand later retrieval.

In sum, conventional digital multimeters incorporate various tools forperforming different types of measurements and different capabilitiesfor displaying measurement values in a digital format on a screen.Further capabilities and improvements are needed, however, in bothhardware and software, to enable users to organize measurementinformation to be obtained by the instrument so as to operate theinstrument efficiently, effectively, and safely.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a front face of a digital multimeter in accordancewith an exemplary embodiment.

FIG. 2 is a schematic layout of various components of the digitalmultimeter.

FIG. 3 illustrates a screen that can appear after a user has selected aMax/Min mode in the digital multimeter.

FIG. 4 illustrates a screen that can appear after a user has selected afunction for measuring milli-volts of direct current (mVDC) in thedigital multimeter.

FIG. 5 illustrates an example of a function and mode menu for thedigital multimeter.

FIG. 6 illustrates a screen displaying a value of a measured temperaturein the digital multimeter.

FIG. 7 illustrates a screen that can appear after a user selects theMin/Max mode by pressing a [MIN MAX] button while the multimeterdisplays the screen shown in FIG. 6.

FIG. 8 is a flow diagram illustrating a method of operating themultimeter when a user moves a rotary switch of the multimeter to a newposition.

FIG. 9 illustrates a screen simultaneously displaying a“mini-measurement” of a live reading and a frozen measurement of a pastreading.

FIG. 10 is a flow diagram illustrating a method for dynamicallygenerating a status bar display in the digital multimeter.

FIG. 11 illustrates an example information dialog displayed on a liquidcrystal display (LCD) screen of the digital multimeter.

DETAILED DESCRIPTION

An inventive digital multimeter and inventive methods for operating thedigital multimeter are disclosed below in detail. The digital multimeterincorporates a rotary switch, a set of keys and buttons, and a digitaldisplay so as to provide highly integrated, programmable andconfigurable features not available on conventional multimeters. Severalof these features, either taken alone or in combination, providesignificant improvements in ease of use, speed of user operation, andsafety associated with use of the digital multimeter. Modifications,alterations, and additions to conventional multimeters that werenecessary to accomplish these features have resulted in benefits thatotherwise would not have been foreseen or appreciated by others skilledin the art.

In one embodiment, a digital multimeter has informative display featuresincluding a display for displaying measurement values and availablefunctions of the multimeter and a user interface for inputting oraccessing information, inputting commands, or browsing through variousmultimeter functions. Graphical icons and/or words presented in thedisplay indicate the potential functions of the multimeter. Themultimeter also usually has a memory for storing information, includingcontext-sensitive explanatory information, information on how to use orperform a function or mode of the multimeter, safety information, andmeasurement data information collected by the multimeter. Thisinformation may be accessed via an information (or Info/“i”) button. Themultimeter also typically has a processor, which retrieves informationfrom the memory and shows the retrieved information on the display.Preferably, the digital multimeter is portable and can informationtransferred to and from an external storage medium, such as an externalcomputer. User input is achieved through actuating one or more buttonsor switches on the multimeter.

A multimeter may present detailed graphical representations of datacollected. For example, the multimeter may represent trends in the data,which can be used for visualizing a large amount of data at once ordocumenting performance of multimeter designs, processes or systems. Itis useful for monitoring and displaying unattended multimeter use, suchthat a user could return to a multimeter and quickly review largeamounts of data, allowing the user to see overall trends and dataanomalies. In one embodiment, a user has the ability to “zoom in” or“zoom out” on graphical trend data to better analyze the data in adesired perspective on the meter screen. Preferably, the multimeter canstore and graph can display at least 5,000 data readings, morepreferably at least 10,000 data readings.

The display of the multimeter may have a display box that appears overthe first display screen, which is called a “pop-up” box. The pop-up boxmay display pictures, graphics, video, charts or text. In onealternative, the text indicates and explains the available functions ofthe multimeter. A user may scroll through information listed on eitherthe main display screen or in the pop-up box with an associatedscrolling mechanism. The pop-up box may also comprise a title bar, whichdisplays information regarding the multimeter functions in operation atthe time when the user input was received. When the pop-up box isdisplayed, the box may also display smaller versions of the measurementvalue or values shown on the larger display screen.

In another embodiment, a digital multimeter presents multiplemeasurements and other information in fonts of various sizes and invarious locations on a multimeter display. The digital multimeter hasmeans, including inputs, for gathering various measurements, includingelectrical measurements and a display, which has various regions orareas within the display. The first region of the display iscentrally-located, i.e., in the middle of the display area, which istypically a screen. The second region is peripherally-located, whichmeans that it may be above, below, or to the side of thecentrally-located region and may abut the centrally-located region. Aprimary reading value of an electrical measurement may appear in eitherthe first region or second region or may be in both regions. In anotherembodiment, the display simultaneously displays both a primary readingvalue of an electrical measurement and another item, which may be aderivative reading value of the electrical measurement, a dialog, amenu, another value or any combination thereof. If the derivativereading value is displayed, the primary reading value and the derivativereading value are preferably based upon the same electrical property.

In a related embodiment, the multimeter display uses a larger font inthe centrally-located (i.e., main) portion of the display than it doesin the peripherally-located portion of the display. The font sizedifference may be any difference such that the centrally-located font islarger, but is preferably larger by at least 25%, and more preferably,larger by at least 50%. If the second region displays the primaryreading value, the first region may display one or more of various typesof information, including a derivative reading value, a dialog, a menu,or a saved measurement value.

The multimeter may also provide ongoing monitoring of dangerouselectrical conditions by showing a warning message on the display. Inone embodiment, the results of the monitoring are displayed in thesecond area of the display. The multimeter can be set or programmed todisplay a warning message accompanying the primary reading value whenthe primary reading value is greater than a predetermined limit. Thisfunctionality provides additional safety for the user because, no matterwhat display is occurring in the center of the screen, the user can beapprised of potentially dangerous situations. The warning message may beany symbol or text which would indicate that the reading has exceededthe preset safety level. In certain embodiments, the warning message isa lightning bolt, flashing text, a flashing status bar, a flashingscreen, a red screen, an alarm sound, such as a repeated beeping, or anycombination thereof so that the warning message causes the user'sattention to turn to the excessive value reading.

In another embodiment, the display may be used to show comparisonsbetween values. For example, the primary reading value may be a relativevalue indicating a difference between an electrical condition and areference value. The primary reading value may be displayed anywhere onthe display, including in the first or second region. Various valuecomparisons may be displayed in both the first and second regionsimultaneously. The display may have an indication, such as an iconaccompanying the value, that the value displayed is a relative value asopposed to an absolute value or a raw measurement.

In yet another embodiment, a digital multimeter comprises a display forshowing measurement values associated with at least one electricalcharacteristic of an electrical circuit, a user interface for receivinga user input to select a mode governing a display format of themeasurement values, a memory for storing an indication of the mode, anda processor for retrieving the indication of the mode from the memory,determining measurement values associated with the electrical circuitbased on input to the multimeter, and generating display data for themeasurement values in accordance with the mode. When the mode is alive-measurement mode, live actual measurement values are displayed in anormal font size in a central portion of the display. However, when themode is not a live-measurement mode, live actual measurement values aredisplayed in a smaller than normal font size in a status bar in aperipheral portion of the display while other measurement values aredisplayed in the central portion of the display. In one embodiment, whenthe multimeter is in a mode that is not a live-measurement mode, thestatus bar at the top of the screen is “inversed,” meaning that whitecharacters in the black status bars turn black and the black backgroundof the status bars turns white or otherwise reverses the contrastbetween the bar background and the text. The status bar may be inversedwhen the meter is in HOLD, AutoHOLD or AutoSAVE mode, when the user isviewing readings from memory (as opposed to live readings), and when arecording, Min Max, or Peak session has been stopped, but has not yetbeen closed. An inversed status bar is designed to provide the user witha visual reminder that the values on the central portion of the displayare not live measurement values.

A multimeter may also store a voltage threshold value in the memory. Avoltage threshold value is an electrical value, a reading above whichmay indicate a dangerous condition in the vicinity of the multimeter.When the processor determines that any live actual measurement valuedisplayed in the status bar is greater than the stored voltage thresholdvalue, a warning message is displayed. As explained with respect to theabove embodiments, the warning message may be any indication that thevoltage threshold value has been reached or exceeded, including flashingwords or symbols, including a lightning bolt, warning colors, warningsounds, or warning words such as “danger” or “threshold exceeded.” Amultimeter may also display live actual measurement values in the statusbar when the mode is a hold mode and a frozen past measurement isdisplayed in the central portion of the display. The multimeter maycomprise a status bar or bars with one or more of a battery strengthindicator, a time, or a date.

Methods of operating digital multimeters of the present invention arealso disclosed. In one embodiment, the method comprises displaying livemeasurements within a main area of a display of the multimeter,detecting whether a user has selected a mode for the multimeter, upondetecting that the user has selected a mode for the multimeter,retrieving from a memory, display parameters corresponding to theselected mode, determining whether the display parameters indicate thatthe live measurements have been removed from the main area of thedisplay, and upon making such a determination, dynamically reconfiguringa status bar within the display to include a smaller-sized or miniaturerepresentation of the live measurements. Methods of using the multimetermay also comprise retrieving a voltage threshold value from the memory,comparing the live measurements with the voltage threshold value, and,if one or more of the live measurements exceeds the voltage thresholdvalue, displaying a warning message on the display, which may bedisplayed in the status bar or in the main display area and may be anyof the warning messages described herein.

In another embodiment, a digital multimeter has a rotary switch memoryand a rotary switch that has more than one position. Preferably, therotary switch will have more than two positions, and more preferably,more than three positions. Each position on the rotary switch isassociated with a “default” primary measurement function, which is thefunction that the multimeter performs or reverts to if the associatedmemory does not store a different function at that position.Additionally, at least one position on the rotary switch is associatedwith one or more non-default primary measurement functions. In oneembodiment, each position on the rotary switch has one default and onenon-default primary measurement functions. Alternatively, each positionon the rotary switch may have one default and multiple non-defaultprimary measurement functions. A further alternative is that somepositions of the rotary switch have only a default primary measurementfunction and other positions have both default and non-default primarymeasurement functions. A multimeter user may control and program themultimeter to accommodate the user's needs.

The multimeter of the present invention has a processor, which allowsfor modification of the primary measurement function selected at a giventime for a position on the multimeter (“active primary measurementfunction”) and a memory for storing such associations. For each positionon the rotary switch, the active primary measurement function may changefrom default to non-default, non-default to default, or from onenon-default function to a different non-default function. The processorprocesses and memory stores the active primary measurement and, when themultimeter is switched to a given position on the switch, the processretrieves the active primary measurement function from the rotary switchmemory and causes the multimeter to perform the active primarymeasurement function. The rotary switch memory may also store a modeassociated with an active primary measurement function, such that themultimeter performs the active primary measurement function inaccordance with the associated mode (such as max/min, hold, etc.)

In certain embodiments, the multimeter stores the active primarymeasurement functions from each position on the switch even when themultimeter is turned off or the multimeter is powered down and thenresumes performance of the active primary measurement function inresponse to the multimeter being turned back on or powered up. In otherembodiments, powering down/turning off the multimeter automaticallyresets one or more of the active primary measurement functions to thedefault primary measurement functions. User input can determine whetherthe active primary measurement is saved or not. The digital multimetermay also have a mechanism for disabling the rotary switch memory, sothat the multimeter only performs the default measurement functionsassociated with a particular position when the disabling mechanism isactivated. The memory still retains its non-default positioninformation, however, and can provide that information to the processorwhen the memory-disabling mechanism is turned off.

In yet another embodiment, the rotary switch memory also stores anactive secondary measurement function associated with the active primarymeasurement function, and the multimeter performs the active secondarymeasurement function in conjunction with performing the active primarymeasurement function. The memory may associate the secondary measurementfunctions with both default and non-default primary measurementfunctions.

The digital multimeter may have a reset mechanism, which clears therotary switch memory. After the reset mechanism is activated, themultimeter will perform the default primary measurement functionassociated with a particular position on the rotary switch. Preferably,reset mechanism has safeguards so that the memory will not be cleared byaccident. The user can also customize the rotary switch in anycombination or permutation of the various functionalities describedherein, including locking the active primary and/or secondarymeasurement functions at certain locations on the rotary switch,preventing the rotary switch memory from storing non-default primarymeasurement functions for selected positions of the rotary switch, andresetting one position of the rotary switch without modifying the activeprimary measurement functions associated with other positions of therotary switch.

In another embodiment, a multimeter is connected to an external centralprocessing unit or computer. The multimeter may be connected to theexternal computer before, during, and/or after use. Transfer of databetween the multimeter and the computer may occur both ways. Forexample, the multimeter can be connected to the computer and thecomputer can download a new set of operating instructions to themultimeter. This is a significant advantage because the multimeter canbe updated with new software programs and new versions of existingprograms without having to replace the memory of the multimeter.Conversely, the multimeter can upload saved data from its memory intothe external computer, thus freeing up more space for additionalmeasurements. If the external computer is connected to the multimeterduring use, the processor of the computer and the processor themultimeter can work in tandem to process the data being acquired by themultimeter. The data acquired can then either be saved to the memory ofthe multimeter or the external computer or both.

Additional optional features of a multimeter include a low impedancevoltage function to prevent false readings due to “ghost voltage.”Separately, a low pass filter function allows test of ac voltage output,and tests for accurate voltage and frequency measurements on adjustablespeed motor drives and other electrically noisy equipment. Finally, a“50 Low Ω” feature allows testing of resistance up to 50 ohms with onemilliohm resolution and is useful for testing motor windings or contactresistance or other areas where making reliable low resistance readingsis required.

The many embodiments of a digital multimeter described herein may beused alone or in any combination or permutation. For example, amultimeter with a rotary switch and rotary switch memory may also have amini-measurement feature and an information button. One skilled in theart will appreciate the variety of features for a digital multimeter,which are further described herein with respect to the figures.

Description of Components in a Highly-Integrated Multimeter Instrument

FIG. 1 illustrates a front face of an example multimeter 100. Multimeter100 typically comprises a compact, handheld body, including contourindentations improving suitability for one-handed operation. The face ofmultimeter 100 is generally characterized by a display 105, a rotaryswitch 120, soft keys 110-113, navigation buttons 114-117, dedicatedbuttons 125-128, and various input jacks 121-124. Multimeter 100 can bepowered by AA alkaline batteries (not shown) or another suitable powersupply.

Measurement Functions and Modes

Multimeter 100 may provide primary measurement functions, such asfunctions for measuring voltage, current, temperature, resistance,electrical continuity, conductance, capacitance, diode test, lowimpedance, low resistance (e.g., 50 Ohms), and AC/DC combinations(“AC+DC”, “AC,DC”). Additionally, multimeter 100 may further providesecondary measurement functions, which are functions for measuringsecondary characteristics of signals or measurements generated by theprimary measurement functions. Examples of secondary measurementfunctions include functions for measuring signal frequency, duty cycle,pulse width, decibels, and crest factor. Although multimeter 100performs only one primary measurement function at a time, it maysimultaneously perform a primary measurement function and one or moresecondary measurement functions.

Multimeter 100 may be set to certain modes that operate in conjunctionwith various measurement functions. These modes determine howmeasurements are acquired and represented without changing themeasurement function. Examples of these modes include “Min/Max,” “Hold,”“Range,” “Peak,” and “Record” modes. “Min/Max” mode is a mode in whichmultimeter 100 displays minimum, maximum, and average measurements thathave occurred over a period of time. In this mode, whenever a newmaximum or minimum occurs—exceeding the previous maximum or minimum—thenew maximum or minimum is stored and displayed. “Hold” mode is a mode inwhich a displayed value is frozen on the display. Manual “Range” mode isa mode in which a range, or resolution, of a displayed value isspecified by user input. Auto “Range” mode is a mode in which a range ofa displayed value is determined by the multimeter. Both Auto Range andManual Range may be accessed via the RANGE button. “Recording” mode is amode in which a sequence of measurements of a parameter is recorded overa period of time for future review or storage. As an example, a sequenceof multiple resistance measurements obtained at different parts of acircuit can be recorded using the “record” mode.

User Input Components—Rotary Switch, Buttons, and Keys

User input components of multimeter 100 include, among other things,rotary switch 120, navigation buttons 114-117, soft keys 110-113,dedicated buttons 125-128, an on/off switch 118 and a backlight controlbutton 119. Dedicated buttons 125-128 (also referred to as dedicatedmode buttons) include an [Info] button 128, a [HOLD] button 125, a [MINMAX] button 126, and a [RANGE] button 127. A user can interact withmultimeter 100 using the various buttons and other features included onthe face of multimeter 100. Additionally, the user's interactions can beguided by information presented on various screens of display 105.Further, multimeter 100 may present the user with output via display105, an indicator light, and/or an audible beeper. Multimeter 100further includes an internal memory for storing information such asmeasurement values.

Soft keys 110-113 are located in an area beneath the display 105 andpositioned to correspond with labels 106-109 on the display. Pressingone of the soft keys 110-113 invokes the command indicated by thecorresponding label on the display. Every screen shown on display 105has a custom set of soft key labels 106-109. Some screens have fewersoft key labels than soft keys. When a soft key label is left blank, thecorresponding soft key is disabled. For example, in the screen shown inFIG. 1, soft key label “Menu” 150 corresponds to soft key “F1” 110, softkey label “Save” 152 corresponds to soft key “F2” 111, soft key label“Setup” 156 corresponds to soft key “F4” 113, and soft key label 154 isleft blank, indicating that soft key “F3” 112 is disabled.

In the example of FIG. 1, navigation buttons 114-117 are centrallylocated among the other buttons of multimeter 100. Navigation buttons114-117 correspond to four cardinal directions: [UP] 115, [DOWN] 117,[LEFT] 114, and [RIGHT] 116. Navigation buttons 114-117 can be used tomove within menus and dialogs and to make choices and perform dataentry. They can also be used to scroll through a sequence of informationtoo extensive to be displayed on a single screen.

[Info] button 128 can provide access to context-sensitive explanatoryinformation about a measurement function and display contents.Additional details regarding [Info] button 128 are discussed furtherbelow. The context-sensitive explanatory information may appear in apop-up information dialog which covers a portion, including most or all,of the underlying screen.

Multimeter 100 may include a backlight for the display 105 to allowimproved viewing in conditions of reduced light. The backlight istypically activated by backlight control button 119. Multimeter 100 canalso include an On/Off button 118 used to turn multimeter 100 on or off.

Rotary switch 120 includes positions 130, 132, 134, 136, 138, 140, 142,144, 146, and 148. Each of these positions corresponds to at least oneprimary measurement function of multimeter 100. These primarymeasurement functions are indicated by symbols about the periphery ofrotary switch 120. Where more than one symbol is located next to asingle position of rotary switch 120, the symbol closest to rotaryswitch 120 corresponds to a default primary measurement function forthat position and any symbols located farther away from rotary switch120 correspond to non-default primary measurement functions for thatposition. For instance, position 142 of rotary switch 120 corresponds toa default primary measurement function for capacitance measurement(indicated by a capacitance circuit symbol), and a non-default primarymeasurement function for diode testing (indicated by a diode circuitsymbol). A user can change the primary measurement function currentlyassociated with a particular position of rotary switch 120 by actuatingspecific buttons on the face of multimeter 100, as will be described infurther detail below.

For explanation purposes, the term “active primary measurement function”will be used to refer to the primary measurement function currentlyassociated with a particular position of rotary switch 120. In otherwords, the active primary measurement function for a particular positionof rotary switch 120 is the function that is performed by multimeter 100when rotary switch 120 is moved to the particular position. As will beappreciated, the active primary measurement function for a particularposition of rotary switch 120 may be a default primary measurementfunction or a non-default primary measurement function.

As indicated by the various symbols around rotary switch 120, multimeter100 may perform several different primary measurement functions. Theseprimary measurement functions may include, for example, AC voltagemeasurement (e.g., from 0 V to 1000.0 V), AC millivolt measurement(e.g., from 0 mV to 3000.0 mV), DC voltage measurement (e.g., from 0 Vto 1000.0 V0, DC millivolt measurement (e.g., from 0 mV to 3000.0 mV),resistance measurement (e.g., from 0Ω to 500.0 MΩ), capacitancemeasurement (e.g., from 0.001 nF to 50 mF), temperature measurement, ACcurrent measurements (e.g., from 0 mA to 20.000 A), AC currentmeasurements (e.g., from 0 μA to 5000.0 μA), DC current measurements(e.g., from 0 mA to 20.000 A), DC current measurements (e.g., from 0 μAto 5000.0 μA).

When rotary switch 120 is set to a particular position, multimeter 100may be set to display a particular screen containing pertinentinformation related to the present primary measurement function. Eachscreen may present one or more menu items related to the present primarymeasurement function. These menu items may be presented by placingspecific names on soft key labels 106-109. Accordingly, a user mayselect from the menu items by pressing the corresponding soft keys110-113. As discussed below with reference to FIGS. 4 and 5, these menuitems may, among other things, allow a user to switch between thedifferent primary measurement functions associated with a currentposition of rotary switch 120.

Dedicated mode buttons 125-128 provide direct single-press access todifferent modes. Pressing [HOLD] button 125 may cause multimeter 100 tohold a currently displayed measurement value. Pressing [MIN MAX] 126button may cause multimeter 100 to capture the highest, lowest, andaverage readings over a period of time. Pressing [RANGE] button 127 maycause multimeter 100 to prompt a user to manually select a desiredmeasurement range. Other modes may be selected by using soft keys110-113 and navigation buttons 115-117 to make selections from menus ondisplay 105.

Multimeter 100 can be turned off and on again without losing itspresently-employed settings. For instance, multimeter 100 can be turnedoff and on again without reverting from a non-default primarymeasurement function associated with a particular position of rotaryswitch 120 to a default primary measurement function associated with thesame position. Similarly, multimeter 100 can be turned off and on againwithout reverting from a non-default mode associated with a particularposition of rotary switch 120 to a default mode associated with the sameposition. Moreover, upon powering up, multimeter 100 can resumeperformance of any previously selected secondary measurement functionswithout requiring additional user input. In other words, multimeter 100preserves specific user-configured settings even when turned off.

When rotary switch 120 changes from a first position to a secondposition, the screen of display 105 changes in accordance with a newmeasurement function associated with the second position. Typically, anymodes or other configurations that have been designated for the firstposition are not maintained when rotary switch 120 changes to the secondposition. For instance, if multimeter 100 performs a first measurementin Hold mode while rotary switch 120 is at a first position, multimeter100 will not necessarily maintain the Hold mode when rotary switch 120is moved to a second position.

Multimeter 100 may receive input signals through probes or other inputsources connected to input jacks 121-124. Multimeter 100 may produceoutput through display 105 and other output interfaces such as indicatorlights or audio sources for generating a beeping noise. Multimeter 100can include an internal memory for storing information such asmeasurement values.

Multimeter User Display

Display 105 may comprise an LCD screen or any other suitable type ofdisplay. In FIG. 1, rotary switch 120 is set to position 132, whichcorresponds to a voltage measurement for an alternating current.Accordingly, display 105 displays voltages measured by this measurementfunction. As shown in FIG. 1, some measurements may be displayed in abold type and/or in a comparatively larger font size in relation toother displayed measurements. Display 105 may further display additionalmeasurements or collateral information related to the displayedmeasurements.

Schematic Layout of Multimeter Circuitry and Components

FIG. 2 is a schematic layout illustrating various components of digitalmultimeter 100 in accordance with one example. In the example of FIG. 2,multimeter 100 comprises a digital display 200, a power source 210,controllers/processors 220, a memory 230, and input components 240, 250,260, an external input interface 270.

Display 200 typically comprises an LCD screen or other suitable display.In some examples, display 200 is characterized as having a smallfootprint of approximately 6-8 square inches. Display 200 includes anarea for a status bar 201 near an upper portion, and a soft keys areafor displaying soft key labels. Display 200 receives data fromcontrollers/processors 220 and power from power source 210.

In some examples, power source 210 comprises batteries to allow forportability. Alternatively or additionally, power source 210 mayincorporate an AC adapter to receive power from a standard AC electricaloutlet. Power source 210 is connected to display 200,controllers/processors 220, and memory 230.

In the example of FIG. 2, controllers/processors 220 include one or moreapplication processors 222 and one or more measurement processors 221.In general, it should be recognized that the functionality ofapplication processors 222 and measurement processors 221 canpartitioned, combined, and implemented in a variety of different ways.For instance, various components of both processors can be implementedon the same chip, or distributed across many discrete and distinctelectrical and/or logical components. Moreover, many components ofapplication processors 222 and measurement processors 221 can beimplemented in various combinations of hardware and/or software.

Application processors 222 typically comprise components for controllingother features of multimeter 100, and for receiving and processinginputs from input components 240, 250, and 260, measurement data frommeasurement processors 221, and stored data from memory 230. Measurementprocessors 221 typically comprise components for capturing measurementdata provided through one or more electrical leads or contacts of inputcomponent 260. Several basic technologies for implementing the functionsof controllers/processors 220 are well known and will therefore not bediscussed in great detail.

Memory 230 typically comprises one or more volatile or nonvolatilememory devices. The one or more memory devices may store and retrievedata using any of several known techniques, architectures, databasesystems, and so on. In general, memory 230 stores information 231 and232 respectively relating to various available measurement functions(e.g., V AC, V DC, ohms, etc.) and modes (e.g., auto-save, relative) ofmultimeter 100. Such information may be used, for instance, to controlthe operation of these functions and modes. Memory 230 further storesinformation 233 related to the state of rotary switch 120 and anycurrent configurations (e.g., non-default primary measurement functions,modes) associated with different positions of rotary switch 120. Memory230 further stores information 234 related to a status barmini-measurement display, information 235 related to voltage thresholdvalues for different modes, and information 236 related to aninformation button of multimeter 100.

Rotary Switch and Rotary Switch Memory

FIGS. 1 and 3-7 illustrate various screens associated with differentpositions of rotary switch 120. The information displayed in thesescreens is described in further detail below.

FIG. 1 illustrates a screen associated with position 132 of rotaryswitch 120. The screen of FIG. 1 displays a measured voltage “123.45VAC”.

FIG. 3 illustrates a screen that appears when rotary switch 120 is inposition 132 and a user presses [MIN MAX] button 126 to invoke theMin/Max mode. The screen of FIG. 3 displays a live voltage “119.8 VAC”(labeled 302), a maximum measurement value “127.09 VAC” (labeled 304),an average measurement value “119.50 VAC” (labeled 306), and a minimummeasurement value “110.23 VAC” (labeled 308). Each of measurement values304, 306, and 308 is accompanied by a time stamp 310 denoting a timewhen the measurement value was detected.

FIG. 4 illustrates a screen displayed when a user selects the defaultprimary measurement function associated with position 138 of rotaryswitch 120. In the disclosed example, the default primary measurementfunction associated with position 138 is a function for measuring mVDC.To access a non-default primary measurement function associated withposition 138, a user may select soft key 110 to access a function andmode menu for changing the primary default function. The menu presentsoptions for alternative primary measurement functions and modes andallows the user to select an alternative primary default function ormode for the current position of rotary switch 120.

FIG. 5 illustrates an example of the function and mode menu that canappear after the user presses soft key 110 in the screen of FIG. 4. InFIG. 5, a user has selected a temperature measurement function by usingnavigation keys 114-117 to highlight a box 504 located next to the label“Temp” as shown in FIG. 5. When box 504 is highlighted, the soft keylabels corresponding to soft keys 110, 111, and 113 show an “F” (alsolabeled 506) for measurement in degrees Fahrenheit, a “C” (also labeled508) for measurement in degrees Celsius, and “close” (also labeled 510)to close the function and mode menu and return to the screen of FIG. 4.

FIG. 6 illustrates a screen that can be displayed after a user pressessoft key 110 when the screen of FIG. 5 is displayed. FIG. 7 illustratesa screen that can appear after a user selects Min/Max mode by pressing[MIN MAX] button 126 while the screen of FIG. 6 is displayed. The screenof FIG. 7 displays a measured voltage “26.5° C.” (labeled 702), amaximum measurement value 29.28 (labeled 704), an average measurementvalue 27.83 (labeled 706), and a minimum measurement value 25.02(labeled 708). The screen of FIG. 7 further displays time stamps 710indicating when the minimum, maximum, and average values were obtained.

Multimeter 100 includes a rotary switch memory (RSM) for storingconfiguration information associated with individual positions of rotaryswitch 120. The RSM may store any non-default primary measurementfunction, secondary measurement functions, and mode used by multimeter100 in conjunction with each position of rotary switch 120. In someexamples, the RSM comprises a non-volatile memory to maintain the storedconfiguration information even when multimeter 100 is turned off.

The RSM operates as follows: When a user moves rotary switch 120 to anew position, multimeter 100 accesses the RSM to determine whether anyconfiguration information has been stored for the new position. If theRSM does not store any configuration information for the new position(or the RSM indicates default configuration information), multimeter 100will perform the default primary measurement function corresponding tothe new position using a corresponding default mode. However, if the RSMstores configuration information for the new position, multimeter 100will perform any primary measurement function indicated by theconfiguration information, and will use any mode indicated by theconfiguration information. Accordingly, if the RSM stores non-defaultfunction or mode information, multimeter 100 will operate in accordancewith the non-default information without requiring the user to accessany menus or press any buttons.

Functions associated with the RSM (hereafter, “RSM functions”), such asfunctions for storing and applying configuration information, can beconfigured and/or enabled or disabled from a setup screen. An examplesetup screen can be accessed by pressing soft button 113 when display105 shows any of the screens illustrated in FIGS. 1, 3-4, and 6-7. Ifthe RSM is disabled, multimeter 100 simply performs a default primarymeasurement function using a default mode each time rotary switch 120changes to a new position. Accordingly, when RSM functions are disabled,a user must access a menu or press a function key to access previouslyused non-default primary measurement functions or modes. A user canreset the RSM so that multimeter 100 will operate using default primarymeasurement functions and default modes for all or some positions ofrotary switch 120. The user can perform this reset from a reset menu,button, or other input interface.

Returning to the example of FIGS. 1 and 3-7, where RSM functions areenabled, a user can switch multimeter 100 from the configuration of FIG.7 (Temperature Measurement, Min/Max display mode) directly to theconfiguration of FIG. 3 (VAC measurement, Min/Max mode) by switchingrotary switch 120 from position 138 to position 132. When rotary switch120 assumes position 132, multimeter 100 accesses the RSM, identifiesthe prior primary measurement function and mode associated with position132, and initiates that primary measurement function and mode.Similarly, a user can switch multimeter 100 back to the configuration ofFIG. 7 by simply moving rotary switch 120 from position 132 to position138.

On the other hand, where RSM functions are disabled and multimeter 100has the configuration of FIG. 3, if a user moves rotary switch 120 fromposition 132 to position 138, multimeter 100 will automatically returnto the screen shown in FIG. 4. In other words, multimeter 100 willassume the default primary measurement function and mode associated withposition 132.

In some embodiments, certain modes or functions may not be affected byRSM functions. For instance, to comply with safety standards, multimeter100 may prevent the RSM from automatically changing the contents ofdisplay 105 based on certain modes. As an example, multimeter 100 mayprevent the RSM from automatically changing the contents of display 105to show only low frequency signals (e.g., in a low-pass filter mode)because a user may mistake the displayed low frequency signals for acomplete live measurement. As a result, the user may fail to appreciatethe possible danger of touching live connections that the user believesto be safe. While multimeter 100 may automatically prevent some modes orfunctions from being affected by RSM functions, multimeter 100 may alsoallow a user to specify certain modes or functions that may or may notbe affected by RSM functions.

Multimeter 100 may be programmed to perform certain procedures involvinga sequence of measurements taken by a user. These procedures may includesteps which require the user to change rotary switch 120 to various newpositions and/or to select non-default primary measurement functions fordifferent positions of rotary switch 120. When RSM functions areenabled, multimeter 100 can store information for the procedure. Forinstance, if the procedure requires the user to perform a sequence ofnon-default primary measurement functions corresponding to differentpositions of rotary switch 120, the RSM memory may store information toallow the user to automatically access these functions without accessingmenus or pressing buttons after moving rotary switch 120. The RSMfunction can also store any information necessary to resume a procedurein cases where the power supply for multimeter 100 is interrupted forany reason in the middle of the procedure.

In some embodiments, RSM functions are permanently enabled to prevent auser from accidentally losing stored configuration information. In theseembodiments, a user may be able to restore default settings for rotaryswitch 120 by pressing a button or by making a selection from a menu.Additionally, in some embodiments, RSM functions may be permanentlyenabled for only some positions of rotary switch 120. In theseembodiments, a user can control whether RSM functions are enabled inpositions for which RSM functions are not permanently enabled.

FIG. 8 is a flow diagram illustrating a method of operating multimeter100 when rotary switch 120 is moved to a new position. In thedescription that follows, example method steps will be denoted byparentheses (XXX). For explanation purposes, it will be assumed that themethod is performed by multimeter 100 under the control of applicationprocessors 222. However, it should be understood that the method may beperformed by other devices or implemented in different ways.

Referring to FIG. 8, application processors 222 detect movement ofrotary switch 120 to a new position (801). Next, application processors222 determine whether RSM functions have been enabled (802), which canbe done, e.g., using a setup menu, as described above. If RSM functionsare disabled (802=No) application processors 222 control multimeter 100to perform the default primary measurement function for the new positionof rotary switch 120 (811). Multimeter 100 then performs one or moremeasurements using the default primary measurement function (808) anddisplays the measurements on display 105 (809).

If RSM functions are enabled (802=Yes), application processors 222retrieve data from the RSM for the new position of rotary switch 120.Based on the retrieved data, application processors 222 determinewhether the most recent primary measurement function performed at thenew position of rotary switch 120 was a default primary measurementfunction or a non-default primary measurement function (804). If themost recent primary measurement function was a default primarymeasurement function (804=No), multimeter 100 performs the defaultmeasurement function (811) and continues to steps 808 through 810.

Otherwise, if the most recent primary measurement function was anon-default primary measurement function (804=Yes), applicationprocessors 222 selects the non-default primary measurement function(805). Then, the application processor determines whether a non-defaultmode was previously enabled in conjunction with the selected non-defaultprimary measurement function (806). If so, (806=Yes), applicationprocessors 222 enable the non-default mode (807), and multimeter 100continues to steps 808 through 810. Otherwise, (806=No), multimeter 100continues to steps 808 through 810, performing measurements anddisplaying the measurements using a default mode for the new position ofrotary switch 120. After completing step 809, application processors 822determine whether rotary switch 120 has been moved to a new position(810). If so (810=Yes), multimeter 100 returns to step 801. If not(810=No), multimeter 100 may take more measurements and display themeasurements by returning to step 808.

Dynamically Generated Status Bar Providing Live Measurement Reading

Digital multimeters commonly are used to perform relatively simplemeasurements of voltage, current, resistivity or other circuitryparameters. When used for this purpose, the instrument typicallydisplays the measured value in a prominent manner on a display screen toapprise a user of the measurement result.

As discussed above, more sophisticated digital multimeters includecapabilities to display measurement information beyond simplemeasurement values, relating to one or more different modes. Forselection of at least some of these modes, the resulting measurementvalue displayed on the instrument is no longer the actual value of thevoltage, current, or resistivity across a node in a circuit. Instead,the displayed value corresponds to a different characteristic of theactual measurement associated with the selected mode.

As an unfortunate consequence of utilizing different modes whenoperating a multimeter instrument, a user may easily be lulled into amisperception that the multimeter display is reporting an actual livemeasurement reading. As an example, while the hold mode is selected, auser may mistakenly believe that a reading reports an actual livemeasurement, instead of being a previously recorded value. In somesituations, such a misperception could prove to be hazardous to theoperator of the instrument.

In an example embodiment of a digital multimeter, an additional displayvalue is provided as a live measurement value to ensure that a user candiscern the live actual measurement. However, because a portable,handheld multimeter incorporates a very small digital screen, displayingthis value could tend to overcrowd the display or otherwise confuse theuser. There thus exists a tension between the advantages of displayingthe live, actual measurement prominently for safety considerations, andarranging the display in a manner for easy use with a quick glance atthe instrument.

In accordance with the exemplary embodiment, a digital multimeterincludes a dynamically generated status bar that provides, in a single,predictable area, dynamically selected information believed to be ofsignificance to a user. As shown in FIG. 1, the status bar may include,for example, a battery strength indicator 158, the time 160 and date162, and some indication of the instrument setting (speaker set “on”)164. Additionally, when necessary, the status bar may include a displayof the live, actual measurement reading, and an icon indicating whethersuch a reading might be considered dangerous, and to be handled withcaution. The status bar(s) may be inversed to indicate a non-livereading. To preserve space on the display screen, the status bar may bepositioned at the top of the screen (as shown in FIG. 1), or optionally,at a side or bottom area of the screen. In some embodiments, thepositioning of the status bar may be configurable by a user.

Accordingly, in some embodiments, a mini-measurement can be displayedautomatically when the primary measurement function's measurement is notdisplayed or is otherwise obscured from view on the screen. As yetanother example, as shown in FIG. 9, a user may select the “hold” modefor freezing the display of a measurement, such that the main area ofdisplay 105 does not report the live, actual reading. As shown in FIG.9, the status bar includes an indication 902 of the hold mode and a“mini-measurement” 904 informing the user of the live reading whiledisplay 105 is frozen with a past reading on hold. The status bar may beinversed to indicate a non-live reading.

As shown in FIG. 9, the status bar displays the live reading with a unitsymbol (e.g., VAC, VDC, etc.) or other indication of the type ofmeasurement being displayed. Additionally, when a measurement obtainedby a secondary measurement function is displayed in the main area ofdisplay 105, the mini-measurement can display a measurement obtained bythe corresponding primary measurement function. For instance, if theprimary measurement function measures the amplitude of an AC signal andthe secondary measurement function measures the frequency of the ACsignal, the amplitude may be displayed in the status bar while thefrequency is displayed in the main area of display 105. In someembodiments, multimeter 100 allows a user to control whether themini-measurement is displayed on display 105.

As an additional safety feature, the mini-measurement may be accompaniedby a mini lightning bolt (mini bolt) if display 105 is displaying aVolts AC or DC and a potentially hazardous voltage is present. The valuethat triggers the mini bolt is preferably factory preprogrammed topreserve the integrity of the safety feature. For instance, a user or amanufacturing process could set the mini bolt to appear when multimeter100 measures a voltage at or above 30 VAC. In some embodiments, the usercan set the minimum voltage or other condition triggering the mini boltto appear, and can alter a factory programmed value.

In some embodiments, primary readings may be accompanied by acomparatively larger lightning bolt (not shown) when a potentiallyhazardous voltage has been measured or multimeter 100 is beingcalibrated. If the mini bolt is displayed and a larger lightning boltaccompanying the displayed reading is obscured, the mini-measurement,the mini bolt, or both may blink. Additionally, the mini-measurement mayblink when high current is present in the A and mA functions to warn theuser that a fuse of multimeter 100 may eventually fail. In someembodiments, a user may be able to set conditions under which the minibolt will appear and/or blink.

FIG. 10 is a flow diagram illustrating a method for dynamicallygenerating the status bar display in accordance with an exemplaryembodiment. For explanation purposes, it will be assumed that the methodis performed by multimeter 100 under the control of applicationprocessors 222. However, it should be understood that the method couldbe performed by other devices or implemented in different ways.

In the method, application processor 222 first detects that a user hasselected a mode for multimeter 100 (1002). Next, application processor222 retrieves display parameters from memory 230 corresponding to theselected mode (1004). Next, the method determines whether the displayparameters indicate that the live measurements have been removed fromthe main area of display 105 (1006). If so (1006=Yes), applicationprocessor 222 dynamically re-configures the status bar on display 105 toinclude a live measurement with a reduced font size, as a“mini-measurement” (1008). Otherwise (1006=No), no re-configurationoccurs unless a user selects a new mode for multimeter 100.

Next, application processors 222 retrieve from memory 230 a thresholdvalue that was configured by the user or otherwise programmed intomemory (1010). Application processor 222 then compares the retrievedthreshold value with a live measurement and determines whether the livemeasurement is above the threshold value (1012). If so (1012=Yes), alightning bolt warning icon is included in the status bar area (1014),and application processors 222 then determine whether a new mode wasselected (1016). Otherwise (1012=No), application processors 222 skip tostep 1016 without including the lightning bolt warning icon in thestatus bar area.

The method of FIG. 10 provides integrated capability to dramaticallyimprove the safety associated with use of a digital multimeter withpotential high voltage or high current circuitry. By dynamicallyre-configuring the status bar area of display 105, multimeter 100 caninclude extra measurement data when needed, but remove this informationfrom an already-crowded display area when the data otherwise would beredundant. Additionally, the method displays a warning icon, such as alightning bolt, to notify a user when a live actual measurement hasexceeded a voltage threshold value that could threaten the user'ssafety. By positioning the warning icon in the status bar area, the usercan quickly and efficiently check whether its status without otherwisedisrupting measurements in progress.

Information Screens

Multimeter users do not frequently carry the instruction manual for themultimeter while using the multimeter. However, as multimeters havebecome increasingly complex and now incorporate a wide variety offeatures, it is often helpful to provide technical information to helpthe users take measurements and interpret the multimeter's output. Forinstance, the information may help a user to remember what a certainicon represents on a multimeter, or how a particular function of themultimeter is used.

To address the user's need for information, multimeter 100 is configuredto display explanatory information about the functions of multimeter 100when a user presses [Info] button 128. In particular, when the userpresses [Info] button 128, multimeter 100 displays explanatoryinformation describing available functions of multimeter 100 andindicating the purpose of visual elements appearing in display 105. Inaddition to or as an alternative to providing descriptions andindications related to the available functions and visual elements indisplay, the explanatory information may also instruct a user how to usethe functions or interact with the visual elements.

The function of [Info] button 128 is described in further detail below.Although the following description presents a dedicated button as a userinput for requesting generation of an information screen, other inputtechniques may be used as an alternative to the dedicated button.

When a user presses [Info] button 128, multimeter 100 displays a pop-updialog box including information regarding the functionality of iconsand other information on display 105. The displayed information may varyaccording to the context at the time [Info] button 128 was pressed. Forexample, [Info] button 128 may be pushed by a user to receive additionalinformation regarding measurement functions such as a function formeasuring the voltage level of a direct current, a function formeasuring a voltage level of an alternating current, a function formeasuring the crest factor of a periodic signal, a function formeasuring the duty cycle of a periodic signal, a function for recordinga sequence of measurements, or a function for choosing a measurementfunction. Because the context can vary with the position of rotaryswitch 120 and various soft key choices, the information displayed canvary according to these variables.

Each screen, menu, and dialog of multimeter 100 potentially can have acorresponding information dialog that can be displayed when a userpresses [Info] button 128. When a menu is shown on display 105, aselected item on the menu can determine the context for the informationdialog. Alternatively, all menu items can determine the context for theinformation dialog.

Multimeter 100 may display information on any of several differenttopics when a user presses [Info] button 128. The topics may include,e.g., instructions for using a function or examples of applications inwhich a user could employ certain functionality available on themultimeter. As one example, a topic could explain what a certain mode ofmeasuring is and when a user would use the mode. Multimeter 100 can befurther programmed by the user to include certain topics in certaincontexts. For instance, a company may have a particular procedure fortaking measurements in a building. The company could program multimeter100 to display an information dialog including instructions forperforming the company's procedure. By relying on these instructions,the operator can perform the procedure without carrying an instructionmanual.

Multimeter 100 can be programmed such that the explanatory informationdisappears after a predetermined amount of time or upon occurrence of acertain event. Once the explanatory information disappears, multimeter100 restores any information that was covered or displaced by theexplanatory information.

FIG. 11 shows an example screen 1100 including an information dialogdisplayed in response to a user pressing [Info] button 128. Theinformation dialog is displayed in place of, or over, currentmeasurements, and thus screen 1100 includes a miniaturized version 1102of a current measurement. Screen 1100 also includes a title bar 1106indicating the context in which [Info] button 128 was pressed. In theexample of FIG. 11, [Info] button 128 was pressed while multimeter 100was configured to perform a function for measuring DC voltage. A list ofspecific topics is provided below title bar 1106.

In the example of FIG. 11, each of the specific topics relates to thecontext in which [Info] button 128 was pressed. More particularly, eachtopic is associated with an icon 1108 and a brief explanation 1110 ofthe icon. Icon 1108 provides an easy way for the user to quicklyidentify a topic. Additionally, icon 1108 can provide an anchor for eachtopic so that a user can switch from topic to topic by navigatingbetween icons 1108 using navigation buttons 114-117. The topics shownmay be listed in order of relevance to the context. When the user isuncertain about an operation or visible element appearing in thedisplay, the user can push [Info] button 128 to learn about theoperation or visible element appearing in the display.

The user can navigate forward and backward between individual topics aswell as between different pages of the information dialog. Soft Key 110can be set to select “Next” 1112, which moves the dialog to a next topicentry. By pressing soft key 110 and looking at icons 1108, the user canmove fairly rapidly to different topics of interest. Soft key 110 can beprogrammed to become disabled once a last topic is reached in theinformation dialog.

Soft key 111 can be programmed to select “Prev” 1114, which causesscreen 1100 to move to a previous topic entry. Soft key 111 can beprogrammed to become disabled once a first topic is reached in theinformation dialog. Soft Key 112 can be programmed to operate to select“More . . . ” 1116 which allows the user to scroll down the informationone page at a time, ignoring topic boundaries. Selecting “More . . . ”1116 can provide a way for the user to continue reading the textaccompanying an icon for a topic when only a portion of the text isshown on the display. Soft key 112 can be programmed to become disabledonce the end of a topic is reached. The down navigation button canperform the same function as soft key 112 when the information dialog ispresent. The up navigation button can perform that opposite function ofthe down navigation button and soft key 112 when the information dialogis present. In other words, the up navigation button can be programmedto provide a way to scroll up the information on the display. The leftand right navigation buttons can be disabled when the information dialogis present.

Soft key 113 can be programmed to select “Exit” 1118, which closes theinformation dialog once soft key 1111 is pressed. There are variousother ways the information dialog can be prompted to close. Forinstance, the user can close the information dialog by pressing [Info]button 128 while the information dialog is present. The informationdialog may also be closed by turning the rotary switch to a new positionor pressing on/off button 118 or one of dedicated mode buttons 125-127.

[Info] button 128 can be pressed in any context. Title bar 1106 canreflect the context within which the button as pressed. Examples of suchcontexts include configurations of multimeter 100 in which it isperforming or ready to perform any of the following functions: “MeasureVolts DC”, “Measure Volts AC”, “Measuring Crest Factor”, “Measuring DutyCycle”, “Recording Measurements”, and “Choosing a Measurement Function”.

The information dialog may be associated with a scrolling memory thatremembers where in the information dialog the user last scrolled duringa previous viewing of the information dialog in the same context. Oncethe user has scrolled to a certain position in the information dialog,the user may toggle between the underlying screen and the informationdialog without losing the user's place in the information dialog. Forinstance, if the user presses [Info] button 128 while measuring VoltsAC, the information dialog can pop up to display the first topic listedin the information dialog. Then, if the user scrolls down theinformation dialog to a fourth listed topic, and then toggles back tothe original screen and subsequently back to the information dialog, theinformation dialog will display the fourth listed topic. In general,toggling can be accomplished by pressing a button on multimeter 100 tochange the screen displayed on display 105.

The overview information displayed when [Info] button 128 is pushed canbe available in a variety of languages. The overview information can bestored in a compressed format to minimize storage requirements andprovide more capacity for storing measurement information.

In the example of FIG. 2, [Info] button 128 may be part of keys/buttoninput 250, which are electrically connected to application processors222. When a user depresses this [Info] button 128, application processor222 retrieves information about the current context of multimeter 100from memory 230. Based on the retrieved context information, applicationprocessors 222 retrieve data from memory 230 to be presented in theinformation dialog on display 200. For instance, application processors222 may retrieve information regarding icons currently displayed onmultimeter 100 or current functions of multimeter 100.

The information dialog presented in display 105 helps a user to takeadvantage of the various capabilities of multimeter 100. The informationdialog is tailored for a small LCD screen provided on multimeter 100.Because multimeter 100 is intended to be portable and self-contained, itis otherwise highly inconvenient to separately carry a user manual.Further, experienced technicians or other users may be unlikely to totea user's manual, but would benefit from information presented in theinformation dialog. By incorporating this functionality with thesoft-buttons, navigational buttons, and other forms of user input, auser can easily navigate through a vast glossary of informationconcerning multimeter 100 to find desired information quickly andefficiently.

As another unique aspect of incorporating [Info] button 128 onmultimeter 100, a company can re-program or tailor the presentation ofinformation from [Info] button 128 to correspond to particular companyprocedures or processes associated with measuring electrical circuits.This highly-innovative feature provides a particular, unforeseen benefitin the context of digital multimeters, since it can be used by a fleetof mobile technicians at remote sites, who may be required to followstrict guidelines provided by a company. In accordance with an exemplaryembodiment, memory 230 can be programmed for customized informationthrough an associated Flash input, USB port, or other interface.

Referring to FIGS. 2 and 3, in an exemplary embodiment, a user canre-program the information to be presented in response to depressing the[Info] button 128 via a screen presented as part of either the Menu orSetup. Via either a Menu or Setup screen accessible through soft keys110-113, the multimeter 100 may prompt a user to connect the instrumentto a PC via a USB cable at port 270, as depicted in FIG. 3.Alternatively, the application processor 222 in multimeter 100automatically may switch into a programming mode upon detecting a USBconnection. Instead of a USB port, port 270 may be adapted to receiveflash memory from which application processor 222 can retrieve data toreconfigure memory section 236. As a further alternative, multimeter 100may include Bluetooth capability to detect a wireless connection fordownloading additional [Info] button data to memory section 236.

Conclusion

Rotary switch memory, mini-measurement display, and Info button glossaryaccess can be integrated into a single multimeter. Alternatively, eachcan be provided separately, or independently. A user of the multimeterconfigures the multimeter to enable or disable the rotary switch memory,the mini-measurement or the Info button.

Many specific details of certain embodiments of the invention are setforth in the description and in FIGS. 1-11 to provide a thoroughunderstanding of these embodiments. A person skilled in the art,however, will understand that the invention may be practiced withoutseveral of these details or additional details can be added to theinvention. Certain well-known structures and functions have not beenshown or described in detail to avoid unnecessarily obscuring thedescription of the disclosed embodiments.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” Additionally, the words “herein,”“above,” “below,” and words of similar import, when used in thisapplication, shall refer to this application as a whole and not to anyparticular portions of this application. Where the context permits,words in the above Detailed Description using the singular or pluralnumber may also include the plural or singular number respectively. Theword “or,” in reference to a list of two or more items, covers all ofthe following interpretations of the word: any of the items in the list,all of the items in the list, and any combination of the items in thelist.

The above detailed description is not intended to be exhaustive or tolimit the invention to the precise form disclosed above. While specificembodiments of, and examples for, the invention are described above forillustrative purposes, various modifications are possible within thescope of the invention, as those skilled in the relevant art willrecognize. For example, while processes or blocks are presented in agiven order, alternative embodiments may perform routines having steps,or employ systems having blocks, in a different order, and someprocesses or blocks may be deleted, moved, added, subdivided, combined,and/or modified to provide alternative or subcombinations. Each of theseprocesses or blocks may be implemented in a variety of different ways.Also, while processes or blocks are at times shown as being performed inseries, these processes or blocks may instead be performed in parallel,or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily those described above. The elements and acts ofthe various embodiments described above can be combined or altered toprovide further embodiments.

These and other changes can be made to the invention in light of theabove Detailed Description. While the above description describescertain embodiments of the invention, and describes the best modecontemplated, no matter how detailed the above appears in text, theinvention can be practiced in many ways. Details of the system may varyconsiderably in its implementation details, while still beingencompassed by the invention disclosed herein.

The terminology used in the Detailed Description is intended to beinterpreted in its broadest reasonable manner, even though it is beingused in conjunction with a detailed description of certain specificembodiments of the invention. Certain terms may even be emphasized;however, any terminology intended to be interpreted in any restrictedmanner will be overtly and specifically defined as such in this DetailedDescription section. In general, the terms used in the following claimsshould not be construed to limit the invention to the specificembodiments disclosed in the specification, unless the above DetailedDescription section explicitly defines such terms. Accordingly, theactual scope of the invention encompasses not only the disclosedembodiments, but also all equivalent ways of practicing or implementingthe invention under the claims.

While certain aspects of the invention are presented below in certainclaim forms, the inventors contemplate the various aspects of theinvention in any number of claim forms. Accordingly, the inventorsreserve the right to add additional claims after filing the applicationto pursue such additional claim forms for other aspects of theinvention.

1. A digital multimeter, comprising: a display for displayingmeasurement values associated with at least one electricalcharacteristic of an electrical circuit; a user interface for receivinga user input to select a mode governing a display format of themeasurement values; a memory for storing an indication of the mode; anda processor for retrieving the indication of the mode from the memory,determining measurement values associated with the electrical circuitbased on input to the multimeter, and generating display data for themeasurement values in accordance with the mode, wherein, live actualmeasurement values of the electrical characteristic are displayed in afirst font size in the display in a live measurement mode, and the liveactual measurement values of the electrical characteristic are displayedin a second font size in the display in a non-live measurement modewhile at least one non-live measurement value associated with theelectrical characteristic is displayed in the display, wherein a warningcondition and the live actual measurement values are displayed in thenon-live measurement mode in response to the live actual measurementvalues exceeding threshold values, and wherein the second font size issmaller than the first font size.
 2. The digital multimeter of claim 1,wherein the memory additionally stores a user-specified threshold value;and a warning icon is displayed near a displayed live actual measurementvalue when the processor determines that the displayed live actualmeasurement value is greater than the stored threshold value.
 3. Thedigital multimeter of claim 2, wherein the warning icon or the displayflashes and/or is accompanied by a warning sound.
 4. The digitalmultimeter of claim 1, wherein the live actual measurement values aredisplayed in a status bar when the mode is a hold mode and a frozen pastmeasurement is displayed in the display.
 5. The digital multimeter ofclaim 1, wherein the display further includes at least one of a batterystrength indicator, a time, and a date.
 6. A digital multimeter,comprising: means for displaying measurement values associated with atleast one electrical characteristic of an electrical circuit; means forreceiving a user input to select a mode governing a display format ofthe measurement values; means for storing an indication of the mode; andmeans for retrieving the indication of the mode from the means forstoring, determining measurement values associated with the electricalcircuit based on input to the multimeter, and generating display datafor the measurement values in accordance with the mode, wherein liveactual measurement values of the electrical characteristic are displayedin a first font size in the means for displaying in a live measurementmode, and the live actual measurement values of the electricalcharacteristic are displayed in a second font size in the means fordisplaying in a non-live measurement mode while at least one non-livemeasurement value associated with the electrical characteristic isdisplayed in the means for displaying, wherein a warning condition andthe live actual measurement values are displayed in the non-livemeasurement mode in response to the live actual measurement valuesexceeding threshold values, and wherein the second font size is smallerthan the first font size.
 7. The digital multimeter of claim 6, whereinthe means for storing additionally stores a user-specified thresholdvalue; and a warning icon is displayed near a displayed live actualmeasurement value when the means for determining determines that thedisplayed live actual measurement value is greater than the storedthreshold value.
 8. The digital multimeter of claim 7, wherein thewarning icon or the means for displaying flashes and/or is accompaniedby a warning sound.
 9. The digital multimeter of claim 6, wherein thelive actual measurement values are displayed in a status bar when themode is a hold mode and a frozen past measurement is displayed in themeans for displaying.
 10. The digital multimeter of claim 6, wherein themeans for displaying further includes at least one of a battery strengthindicator, a time, and a date.